Black slimy substance from well

I've been having issues for a while with some type of slimy black material coming from my well. I bleached the well and it's still there. Some folks have said it could be manganese; someone else looked at it said it was some type of algae.

The previous homeowner planted a number of trees near the well. There are bunch of smaller trees within 5 feet and then a large pear tree about 8 feet away. The pear tree is directly over the line that would run from the well to the house. Could this be causing an issue or possible leak? Everyone I ask this to acts like I'm crazy but I feel like something is getting into the water. When I changed the filter last time, there was multiple handfuls of this slimy black stuff. (This was after chlorinating this past summer). (The previous homeowners told us they only drank distilled water which seemed odd at the time but maybe now I know why).

Also, i currently have a small whole house filter and use a 5 micron carbon filter. The well company recommended going to a large filter (20 x 4.5). What would be the benefit of that since I would still be using a 5 micron carbon filter (just larger).

The results of my water test were fine. The unfiltered water showed .081 ppm manganese and the filtered water showed 0. They also noted a light odor in the water that came before the filter.

Thanks for any advice. I know nothing about this so just want to make sure installing the bigger filter is the right thing to do.

I have also been told I have manganese in my well water. It's only visible if I get air in the system, when i see the black slimy stuff in my sink or tub.

Like most things, manganese is very small amounts is beneficial (actually essential). It is not harmful to health in drinking water until over .3 to .5 mg/l (similar to ppm). The EPA recommends keeping it below .05 mg/l for "aesthetic" reasons (to prevent stains, taste, odor).

Water softeners will remove some low amounts of manganese. Filters may remove a little. Opinions on this forum run the gamut. Your source probably suggested a larger filter so you won't have to change it as often. If you want "distilled" water, you can install an under-sink RO (reverse osmosis) system for drinking water.

This stuff could be algae. Especially if the filter you have is exposed to sunlight. Algae will grow in PVC pipes in sunlight. An other thing that causes black scale is Hydrogen Sulfide which usually is accompanied by a rotten egg odor. It's not bad for you, it just smells bad.

I have no use for in line filters because they remove very little if anything that could be harmful to you. They just make the filter manufacturer wealthy. You say you had your water tested, what did they test for?

The depth of your well may have something to do with this. Is it a deep well or a shallow well of less than 20 feet?

Thank you for the replies. The well is 200 feet deep.

I had a plumber come out today and look at it. Prior to seeing it, he felt like it was most likely manganese. After seeing it, he said "I've never seen that before. I have no idea what that is." He took a sample to send out for further testing. He said it almost looked like leaves in the water. That reminded me that after we first moved into the house in August 2011, the cap was left off the well for several months. I believe it was left off by the home inspector prior to the sale. Due to the location of the well I did not notice it until several months later when I was cutting back bushes and other landscaping in that part of the yard.

I immediately bleached the well at that time before putting the cap back on. I can't imagine that many leaves could have fallen in to where I am still having problems 6 years later but I don't know what is going on. Here is what the first water test showed:

7.14 pH
3 gpm Hardness
0.15 ppm Iron
0.081 ppm Manganese
100 ppm TDS
0 Nitrates—

The PH is a little low and the hardness being only 3 gpg is amazing. Most well water I'm familiar with is in the 12 to 17 gpg range. No worries with iron or manganese though. TDS is very low.